Evening Terminator(glossary entry)
The Moon's terminator makes a complete circle around the Moon's globe. However, along one half of this arc the passage of the terminator brings sunlight, and on the other half it brings darkness. The Evening Terminator is the arc along which the Sun is setting. The one along which the Sun is rising is referred to as the Morning Terminator. - Jim Mosher
See also: Saber's Beads, which is a curious optical phenomenon related to the very old (and extremely thin) moon's crescent. During the appearance of Saber's Beads, the location of the Evening Terminator is very near the moon's western limb (only a couple of hours before New Moon). Saber's Beads are also observable at the very YOUNG moon's crescent, shortly after New Moon (the Morning Terminator near the moon's EASTERN limb). - DannyCaes Feb 12, 2008
All books about the moon and lunar observing.